在DataGuard环境中如果我们在做failover的时候,可能会碰到ORA-00261错误,下面是该错误的产生原因和解决方法。 如果是由于网络问题而导致需要切换,那么通常standby端的RFS进程并不会意识到primary已经不可访问,所以RFS进程也不会释放当前的standby redo log文件。 如果是primary端的数据库实例由于故障中断,那么一般情况下standby端的RFS进程会立刻意识到primary已经不可访问,也就会立刻释放当前的standby redo log文件。 只要RFS进程没有释放standby redo log文件,那么执行ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH命令就会在alertlog文件中发现如下的报错信息 Warning: log 4 of thread 1 is being archived or modified Recovery interrupted. Media Recovery failed with error 261 如果在报上述错误的时候,执行SWITCH,那么将会出现下面的错误: ORA-16139: media recovery required
所以必须检查alertlog文件,直到发现如下信息才表示RFS进程已经释放了standby redo log文件,这时候才可以作FINISH: RFS: Possible network disconnect with primary database
促使RFS进程释放standby redo log 文件有两种方法: 1. 等待RFS进程的network timeout,通常需要等待8分钟左右 2. 关闭standby数据库,再重新开启,这样会强制RFS进程释放standby redo log 我们可以通过v$managed_standby视图来监控RFS进程何时释放
实行Failover: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH; alertlog中将显示如下信息,表示finish成功: Terminal Incomplete Recovery: UNTIL CHANGE 3738452 Terminal Incomplete Recovery: End-Of-Redo log allocation Terminal Incomplete Recovery: log 4 reserved for thread 1 seq# 8772 TERMINAL RECOVERY changing datafile format version from 8.0.0.0.0 to 9.0.0.0.0 Switching logfile format version from 8.0.0.0.0 to 9.0.0.0.0 Terminal Incomplete Recovery: clearing standby redo logs. Terminal Incomplete Recovery: thread 1 seq# 8772 redo required Terminal Incomplete Recovery: End-Of-Redo log /global/oradata/ctsdb/stdby_redo04.log Identified end-of-REDO for thread 1 sequence 8772 Terminal Incomplete Recovery: end checkpoint SCN 3738453 Media Recovery Complete Switching logfile format version from 9.0.0.0.0 to 8.0.0.0.0 Terminal Incomplete Recovery: successful completion Begin: Wait for standby logfiles to be archived Wed Sep 1 13:42:28 2004 ARC1: Evaluating archive log 4 thread 1 sequence 8772 Wed Sep 1 13:42:28 2004 ARC0: Evaluating archive log 4 thread 1 sequence 8772 Wed Sep 1 13:42:28 2004 ARC1: Beginning to archive log 4 thread 1 sequence 8772 Wed Sep 1 13:42:28 2004 ARC0: Unable to archive log 4 thread 1 sequence 8772 Wed Sep 1 13:42:28 2004 Creating archive destination LOG_ARCHIVE_DEST_1: '/global/oradata/ctsdb/archive/arch1_8772.log' Wed Sep 1 13:42:28 2004 Log actively being archived by another process Wed Sep 1 13:42:28 2004 ARC1: Completed archiving log 4 thread 1 sequence 8772 Wed Sep 1 13:42:43 2004 End: All standby logfiles have been archived Resetting standby activation ID 4038461969 (0xf0b60a11) Completed: ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH
FINSH成功之后再执行SWITCH: ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
SWITCH成功之后,重新启动数据库: SHUTDOWN IMMEDIATE; STARTUP;

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